🎨 Convert to a header-only library (#6)

.github/workflows/main.yml

@@ -0,0 +1,21 @@
+name: Build & Test
+on: [ push, pull_request ]
+jobs:
+  build:
+    name: Testing on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, windows-latest, macos-latest ]
+    steps:
+      - uses: actions/checkout@v1
+
+      - name: Configure
+        run: cmake -DBUILD_TEST=ON .
+
+      - name: Build
+        run: cmake --build .
+
+      - name: Test
+        run: ctest -C Debug .